More than 50 people gathered in Canton’s library Tuesday to hear the results of an independent consultant’s report on a potential 348-unit housing development on the downtown Plymouth Rubber site. The report covered traffic implications, feasibility, environmental effects, and the fiscal effect upon the town. According to the report, the best-case fiscal scenario would be a net gain of about $31,000 in tax revenue, while the worst-case scenario would be a net loss of $277,000. Selectman Robert Burr said Town Meeting would likely get to vote on a zoning change that would allow the project in the fall.